Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1035330AbdD1Avy (ORCPT ); Thu, 27 Apr 2017 20:51:54 -0400 Received: from mail-pf0-f174.google.com ([209.85.192.174]:35874 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1034055AbdD1Avr (ORCPT ); Thu, 27 Apr 2017 20:51:47 -0400 Date: Fri, 28 Apr 2017 09:51:39 +0900 From: AKASHI Takahiro To: Thiago Jung Bauermann Cc: dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kexec: allocate buffer in top-down, if specified, correctly Message-ID: <20170428005135.GA3963@fireball> Mail-Followup-To: AKASHI Takahiro , Thiago Jung Bauermann , dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org References: <20170426082209.12127-1-takahiro.akashi@linaro.org> <1605356.Vp6YPvtjly@morokweng> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1605356.Vp6YPvtjly@morokweng> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1405 Lines: 43 Thiago, Thank you for the comment. On Thu, Apr 27, 2017 at 07:00:04PM -0300, Thiago Jung Bauermann wrote: > Hello, > > Am Mittwoch, 26. April 2017, 17:22:09 BRT schrieb AKASHI Takahiro: > > The current kexec_locate_mem_hole(kbuf.top_down == 1) stops searching at > > the first memory region that has enough space for requested size even if > > some of higher regions may also have. > > kexec_locate_mem_hole expects arch_kexec_walk_mem to walk memory from top to > bottom if top_down is true. That is what powerpc's version does. Ah, I haven't noticed that, but x86 doesn't have arch_kexec_walk_mem and how can it work for x86? > Isn't it possible to walk resources from top to bottom? Yes, it will be, but it seems to me that such a behavior is not intuitive and even confusing if it doesn't come with explicit explanation. > > This behavior is not consistent with locate_hole(hole_end == -1) function > > of kexec-tools. > > > > This patch fixes the bug, going though all the memory regions anyway. > > This patch would break powerpc, because at the end of the memory walk kbuf > would have the lowest memory hole. > > If it's not possible to walk resources in reverse order, then this patch needs > to change powerpc to always walk memory from bottom to top. So I would like to hear from x86 guys. Thanks -Takahiro AKASHI > -- > Thiago Jung Bauermann > IBM Linux Technology Center >